Sperm counts in men worldwide are falling at an alarming rate which, if continued, could spell the end of the human race. The claims come following a review – one of the largest of its kind – of almost 200 studies to assess the fertility of more than 40,000 men from 1973 to 2011.

Experts warn that modern lifestyle factors – including diet, stress and pollution – could be behind the worrying trend, which has seen a 60% plunge in the sperm counts of men living in the West in the space of just 40 years.

A Western worry?

Men from Europe, North America, Australia and New Zealand have suffered the heaviest decline (59.3% drop in sperm count and 52.4% drop in sperm concentration), while those living in South America, Asia and Africa did not display any significant change.

The researchers who worked on the study said the rapid decline showed no sign of 'levelling off' any time soon, and have called for urgent research into the possible causes of the fall. Writing in the journal Human Reproduction Update, the team said:

"Sperm count and other semen parameters have been plausibly associated with multiple environmental influences, including endocrine disrupting chemicals, pesticides, heat and lifestyle factors, including diet, stress, smoking and body-mass index."

They continued:

"Therefore, sperm count may sensitively reflect the impacts of the modern environment on male health throughout the life course."

Some chemicals have previously been associated with lowered sperm counts, including some used to make certain plastics. A diet high in caffeine, processed meat, soy and potatoes is also thought to adversely affect male fertility. Speaking to the BBC, lead researcher and epidemiologist Dr Hagai Levine said:

"If we will not change the ways that we are living and the environment and the chemicals that we are exposed to, I am very worried about what will happen in the future. Eventually we may have a problem, and with reproduction in general, and it may be the extinction of the human species."

Reliable research?

Despite the vastness of the review, it seems that many experts (including those involved in the research process) believe the findings to be flawed in some way. For example, it was highlighted that less developed continents had far fewer studies to contribute, and it is thought that early methods may have resulted in overestimated stats.

However, some of the deficiencies have been accounted for and many believe that – even when taken with a pinch of salt – these findings are significant. Professor Daniel Brison, scientific director of the Department of Reproductive Medicine at the University of Manchester, said:

"The extent of the decline in sperm counts in the Western world revealed in this study is shocking… As the authors point out this has major implications not just for fertility but for male health and wider public health. An unanswered question is whether the impact of whatever is causing declining sperm counts will be seen in future generations of children via epigenetic or other mechanisms operating in sperm."

It is clear that much more research needs to be done before any concrete recommendations can be made. But, for those of you who are concerned by these findings, Dr Levine suggested some practical steps – including "continued efforts on tackling smoking and obesity."

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